random notes of a skeptical geologist

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Here are three photos that demonstrate how well some animals ‘know’ the composition and grain size of the sediment of their homeland. In all three cases, the salt-and-pepper sand of the background is the result of dark-colored grains of volcanic origin mixing with light-colored fragments of corals and seashells.

Ghost crab on Big Island, Hawaii

Ghost crabs are common on many beaches around the world; below is another one from Costa Rica. Note how the different grain size and sediment color are perfectly captured by the crabs.

Ghost crab near Playa Conchal, Guanacaste, Costa Rica

The third example takes us back to Hawaii, under water, where I managed to get this shot of a flounder while snorkeling in Kona. The only reason I saw this guy was that I got really close and part of the seafloor, which later turned out to be the flatfish, unexpectedly took off.